feat: inject session mode into persona system prompt

context_loader.load_context() now accepts a mode param ("chat"|"otr").
In OTR mode, the --- System --- block gains a second line:

  Current mode: Off The Record — this conversation is private
  and will not be logged or included in memory distillation

routers/chat.py passes mode="otr" when req.off_record is True.
Normal chat and all orchestrator calls stay at mode="chat" (no change
to the System block). The System block consolidates date/time and mode
in one place, matching the existing timestamp pattern.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cortex/context_loader.py

@@ -21,6 +21,7 @@ def load_context(
     include_short: bool = True,
     role_append: str = "",
     inject_datetime: bool = True,
+    mode: str = "chat",
 ) -> str:
     """
     Build the system-prompt context block for a given tier and memory toggles.
@@ -39,10 +40,18 @@ def load_context(
     inara_dir = persona_path()
     parts = []
 
-    # ── 0. Current date and time (per-role toggle — injected first so it's prominent) ──
+    # ── 0. System block — date/time and session mode (injected first so it's prominent) ──
+    system_lines = []
     if inject_datetime:
         now = datetime.now().astimezone()
-        parts.append(f"--- System ---\nCurrent date and time: {now.strftime('%A, %Y-%m-%d at %I:%M %p %Z')}")
+        system_lines.append(f"Current date and time: {now.strftime('%A, %Y-%m-%d at %I:%M %p %Z')}")
+    if mode == "otr":
+        system_lines.append(
+            "Current mode: Off The Record — "
+            "this conversation is private and will not be logged or included in memory distillation"
+        )
+    if system_lines:
+        parts.append("--- System ---\n" + "\n".join(system_lines))
 
     # ── 1. Core identity (always) ──────────────────────────────────
     for filename in _CORE: